Various joining methods are known for joining a bump electrode of an electronic component to an electrode of a printed circuit board.
For example, an ultrasonic joining method, which is one of such joining methods, is able to join electronic components to a circuit board in a short time.
Here, the ultrasonic joining method is a joining method that allows, while pressing an electronic component against a circuit board, the electronic component to vibrate by ultrasonic vibration so as to join electrically an electrode of the electronic component to an electrode of the circuit board at the atomic level, using bonding by destruction and dispersion of the surface coating generated by a local slip in the joining face.
Now, referring to FIG. 10, the constitution and operation of a conventional bonding tool 9 that uses the above-mentioned ultrasonic joining method is described.
Further, FIG. 10 is a schematic front view of the conventional bonding tool 9.
The conventional bonding tool 9 is an apparatus for allowing an electronic component 8 to vibrate by an ultrasonic vibrator 52 so as to carry out bonding of the electronic component 8 to a circuit board 81 (for example, see Japanese Patent No. 3788351).
The bonding tool 9 comprises a horn 91, the ultrasonic vibrator 52, and an electronic component holding part 93.
The electronic component holding part 93 has a male fitting part 932 in the shape of a stumpy column, a female fitting part 9151 in the shape according to the shape of the male fitting part 932 is formed in the horn 91, and the male fitting part 932 is fitted into the female fitting part 9151 via an adhesion layer 916.
In the description hereinafter, the X axis, the Y axis and the Z axis for defining an orthogonal coordinate system in three dimensional space, which are orthogonal to each other, are used.
The horn 91 is substantially a prism in shape, whose longer direction is the X direction in which ultrasonic vibration is transmitted. The horn 91 has a symmetry plane S1 parallel to the YZ plane, a symmetry plane S2 parallel to the XY plane, and a symmetry plane S3 (not shown) parallel to the ZX plane.
The female fitting part 9151 in the shape according to the shape of the male fitting part 932 is formed in a horn protruding part 915 that is provided on the lower face among the two faces of the horn 91 parallel to the XY plane, which is on the (−Z) side. The female fitting part 9151 is a groove whose cross-sectional shape is rectangular.
The electronic component holding part 93 comprises the male fitting part 932 in the shape of a prism, and an electronic component holding face 5311 being provided on a tip end part 531, which holds the electronic component 8 on the opposite side to the male fitting part 932. The male fitting part 932 is a ridge whose cross-sectional shape is rectangular.
Here, mainly referring to FIGS. 11 and 12, the constitution is described in more detail in which the male fitting part 932 of the electronic component holding part 93 is fitted into the female fitting part 9151 of the horn 91 via the adhesion layer 916.
Further, FIG. 11 is a schematic front view of a vicinity of the electronic component holding part 93 of the conventional bonding tool 9. Moreover, FIG. 12 is a schematic front view of a vicinity of the electronic component holding part 93, to which ultrasonic vibration is being given, of the conventional bonding tool 9.
The male fitting part 932 has a top face F93, and side faces F93′ and F93″.
The female fitting part 9151 has a bottom face F91, and side faces F91′ and F91″.
Manufacture of the bonding tool 9 is able to be carried out by arranging a brazing material for forming the adhesion layer 916 between the male fitting part 932 and the female fitting part 9151, forming the adhesion layer 916 by heating the male fitting part 932 and the female fitting part 9151 with pressurization, and fitting the male fitting part 932 into the female fitting part 9151. For example, a thin sheet-like brazing material can be stuck on an adhesion face of the male fitting part 932 or the female fitting part 9151, so that the brazing material is melted through increase of the temperature with the electronic component holding part 93 and the horn 91 being sandwiched with pressurization and the temperature is decreased afterward.
Here, in order to easily perform the process of inserting the male fitting part 932 deeply into the female fitting part 9151 in a state where the thin sheet-like brazing material is stuck on the adhesion face as mentioned above, sufficient clearance has to be ensured beforehand between the male fitting part 932 and the female fitting part 9151.
On that account, the width W93 of the top face F93 has to be sufficiently smaller than the width W91 of the bottom face F91.